TAKE-HOME - PLSC 400 Environmental Plant Physiology...

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PLSC 400 4/17/2008 Environmental Plant Physiology Second Exam Name: __ Erik Kramer _______________ 1. (10) Solar Radiation a. How are photons of electromagnetic radiation generated in the core of the sun? Nuclear fusion reactions in the core produce Helium atoms by fusing Hydrogen atoms. Energy is released from this reaction in the form of Gamma radiation b. Visible Radiation is divided into a number of spectral regions. What type of light is defined by the following wavelength ranges: 500 – 600 nm ____Green __ 320 – 400 nm ____ UV-A _______ 700 – 800 nm ____ Far-Red ____ 400 – 500 nm ____ Blue ________ 290 – 320 nm ____ UV-B ______ c. When a photon is absorbed by a molecule what happens to the energy of the photon and what happens to the molecule that absorbs it? 100 percent of the photon’s energy is absorbed by the molecule, which causes an electron to become excited and jump to an outer orbital (excited state). The energy from this high-energy state can be used to facilitate reactions or is dissipated as heat or re-emitted at a longer wavelength. d. What are two examples of pigment molecules and why are they able to absorb visible radiation? Chlorophyll, Carotenoids. The molecular structure of these molecules determines their ability to absorb certain portions of visible radiation. The ring structures and conjugated double bond systems result in high electron density allowing them to absorb the low-energy photons of visible radiation. 1
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e. What is the relationship between the energy of a photon of blue light and a photon of red light? Photons of red light have a lower energy than photons of blue light because red light has a longer wavelength. 2. (20) Photosynthesis: Thylakoid Reactions a. Describe the composition of the Core Complex and Reaction Center of Photosystem II The Core Complex is embedded in the thylakoid membrane and is composed of a water-oxidizing site on the lumen-side of the membrane, a plastoquinone reductase site on the stroma-side of the membrane. It also contains a set of chlorophyll and pheophytin chromophores. The Reaction Center consists of a multisubunit protein supercomplex, including the D1 and D2 membrane proteins which have associated chlorophyll, pheophytin, and plastoquinone molecules as electron acceptors. b. How is light absorbed by the Light Harvesting Complex of Photosystem II ? Photons excite electrons of pigment molecules of the antenna complexes (Carotenoids, Chlorophyll a and b ), which transfer the energy to the P680 antenna pigment of the PSII reaction center on the stroma-side of the membrane, causing P680 to be excited. P680 can also directly absorb photons of specific wavelengths. c.
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TAKE-HOME - PLSC 400 Environmental Plant Physiology...

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